1. Field of the Invention
This invention relates to method and apparatus for the manufacture of consolidate sheeting material, commonly termed particle board, made from particles and/or fibers of wood or other organic substances
2. Prior Art
Particle board which, conventionally, is produced by pressing a mat of resin-coated fibrous material, such as wood fibers and the like, is when subject to moisture in use, prone to thickness swelling. It has been found (see United States Forest Service Research Note FBL-0187 March 1968) that treating finished particle board with steam at about 360.degree. F. for 10 minutes reduces the tendency of particle board to swell under moist conditions and as a result of said finding, the processes of using steam have been developed for adoption in the manufacture of particle board. These processes have, in the main, involved the application of pressurized steam to one side surface of the particle board after the fibrous mat is compressed. After the steam pressure builds up to the required temperature, steam is allowed to escape from the opposite side surface of the board so as to allow the added moisture to escape from the board. This process, particularly with respect to thick boards, results in a greatly decreased manufacturing time due to the rapid setting of the resin in the center of the board.
A process of this nature requires that the fibrous material, in a loose mat, first be laid on a foraminous caul and then the caul and the fibrous mat positioned between a pair of platens through which steam can be injected and extracted while the platens apply pressure to opposite sides of the mat. This process, and apparatus to carry out this process, has some draw-backs. Firstly, unless the press equipment includes a caulless type transfer system, a preferrable caul for this type of process is formed of a wire mesh which is difficult to load in the press due to lack of rigidity and is subject to deformation unless great care is taken in positioning it between the platens. Secondly, this process does not lend itself to multiple sheet production as apparatus requires application of steam to one surface of particle board being one of a plurality of boards being pressed at one time and exhaustion from an opposite side surface of each of the particle boards, is complicated and thus costly.